Silicone oil supply webs are known which provide a release agent to a fuser in an electrophotographic process such as that used in electrophotographic printers. Such printers produce hardcopy images on paper or other print media through precise deposition of toner onto the paper. The toner is adhered to the paper by a fuser hot roller, which heats and melts the toner to fuse it to the paper. As the toner melts, it becomes tacky and has a tendency to adhere to the fuser hot roller. Over time, accumulated toner can compromise the print process. Application of a lubricating substance such as silicone oil to the fuser hot roller serves to prevent adhesion of the toner, and also smooths the toner surface on the paper. An oil supply web provides a controlled supply of silicone oil to a fuser hot roller during the print process.
Referring to prior art FIG. 1, an oil supply web 10 is a sheet of fibrous or membrane material held against the fuser hot roller 18 by an idling bias roller 20. The web is wrapped around a supply roller 12 and a take-up roller 14. Oil delivery is controlled by indexing the take-up and supply rollers 14, 12 as the web is held against the fuser hot roller by the bias roller 20. As the web 10 is fed in a direction opposite to the rotation of the fuser hot roller, abrasive and frictional forces clean the fuser hot roller 18. Since the fuser hot roller 18 rotates in a direction opposite to the web 10, the web remains taut between the idling bias roller 20 and the take-up roller 14. Concurrently, silicone oil absorbed or embedded in the web is applied onto the fuser hot roller upon contact therewith as the paper 22 advances. A controlled supply of oil is therefore provided to the fuser hot roller as the web advances from the supply roller 12 to the take-up roller 14.
The oil supply web 10, however, can become unraveled when the fuser hot roller is rotated in a reverse direction. Reverse rotation can result from attempts 1o clear paper jams. Referring to prior art FIG. 2, reverse rotation can occur from a user removing paper 24 in the direction of arrow 26, or from rotation of a jam-clearing knob 28. Frictional contact between the web and the fuser hot roller due to the idling bias roller 20 occurs as the fuser hot roller 18 rotates in the reverse direction. Such reverse rotation causes the web 10 to unravel from the supply roller 12 into the jam zone 30. Unraveling of the web causes the web material to jam, decreases the web supply lifetime, and can also cause further problems if excess oil leaks onto other parts.
It would be beneficial, therefore, to provide an apparatus which prevents the oil supply web from unraveling when the fuser hot roller is rotated in a reverse direction, yet which does not hinder the rotation of the fuser hot roller in the normal direction, so as to allow both normal or jam-clearing hot roller rotation without compromising the oil supply web.